Particle distribution plotting apparatus



July 18, 1967 COULTER ET AL 3,331,950

PARTICLE DISTRIBUTION PLOTTING APPARATUS Original Filed Feb. 27, 1961 4Sheets-Sheet 1 5 EEME E a m an A? a a 52:5 5 w m a $555 $3 HES E5 T m@ WL IH- w w W Lv v l I. I. 8 mm H A. m m E L.P 3s EMF 5 m 5, at B E n 2 ad W c E .W I A mi m SE 3W EiE fiiaE 19 2% 53% 5E 5 m& QQ m QQ Gm II Angm 1 m fifi l fiw I 55 I IMMW I 6% sum 6% 6R m Q A ATTYS.

y 18, 1967 w. H. COULTER ET AL 3,331,950

PARTICLE DISTRIBUTION PLOTTING APPARATUS original Filed Feb. ,27, 1961 4Sheets-Sheet 4 N0. of Pam's/e5 PHI/IC/E Size No. of Parfic/es Par/IsleSize INVENTORS Wa/lace H Cou/fer Abra/vam S/ge/man United States PatentClaims. (Cl. 235-92) This application is a continuation of ourco-pending application Ser. No. 92,006, filed Feb. 27, 1961, nowabandoned.

This invention relates generally to the art of detecting and sizingparticles of minute dimensions maintained in suspension in some carrierfluid, and more particularly, is concerned with the provision ofapparatus which will plot automatically, on a suitable chart, forinstance, certain information relative to the distribution of sizes andquantities of particles in the suspension under study.

The techniques of counting and sizing particles are utilized in greatand diversified scope in many sciences and industries. There are manydifferent devices and equipment which are utilized for such purposes,from the various optical devices which are operated manually andtediously to the complex and sophisticated machines which operateelectronically. Considerable advance in the field has been achieved byapparatus constructed in accordance with U.S. Patent 2,656,508, and animproved apparatus constructed in accordance with US. Patent 3,259,842;both foresaid patents being owned by the assignee of this application.

In said patented apparatus, the particles are caused to pass through amicroscopic or macroscopic aperture so as to vary the conductance of thevolume of carrier or suspension fluid contained along the length of theaperture. Means are provided to detect such changes and thereby provideelectrical signals, each representing a particle, and the amplitude ofthe signal for any particle being substantially proportional to the sizeof the particle. The earlier apparatus was provided with counting meansenergized by the signals. An intervening threshold circuit enabled theoperator to limit the signals reaching the counting apparatus to thosewhich had amplitudes only greater than the threshold. The thresholdamplitude could be varied, so that this apparatus could be used forsizing particles as well as counting them.

The improved apparatus described and claimed in said co-pendingapplication has many changes in the circuitry, although it operates onsubstantially the same principles. In addition, in its circuitry, thereis included a pair of threshold circuits, each of which may be adjustedto provide an independent threshold value. The signals provided bydetecting the passage of particles through the aperture are screened bythe two threshold circuits whereby only those signals will pass throughthat are of an amplitude lying between the levels established by the twothresholds. In effect, therefore, the threshold circuits provide awindow, the upper and lower limits of which are adjustable, so that onlyparticles of a given size range are counted for any given window. Ifdesired, the upper threshold limit circuit can be completelydisconnected to enable particle counts for all sizes above the lowerthreshold limits.

It Will be appreciated from the information given above that using thesecond mentioned structure, it is possible to obtain data which willenable the plotting on charts of the distribution of various particlecharacter istics for any given suspension, but notwithstanding the vastimprovement over all previously known apparatus, when using theaforementioned apparatus, is required to be done slowly and manuallyfrom the information given. For each reading it is required to adjustthe threshold circuits to the new window limits, and this is, requiredto be done manually. Although a considerable time saving occurs overthat previously necessary to secure such charts, the time interval isstill suchas to discourage the making of such charts or graphs as aroutine matter.

The invention herein is concerned with apparatus that can be connectedwith the structures of the above described patent and application orother particle detection apparatus, such as optical detectors, for thepurpose of providing automatic plotting. It provides such rapid andfacile plotting of the relative distribution of particle characteristicsas to enable the making of graphs illustrating the same as a matter ofroutine in the operation of the particle detecting apparatus.

The apparatus of this invention achieves several unique functions whichmay be enumerated as follows:

(a) The apparatus can be adjusted to plot a graph which gives therelative distribution of particles of different sizes in a givensuspension.

(b) The apparatus can be adjusted to plot a graph of the total number ofparticles of a given size in a suspension between any two limits definedby a window.

(0) The apparatus can be adjusted to plot a graph which gives therelative distribution of particles of certain selcted sizes.

(d) The apparatus can also be used to indicate particle flow rates.

In essence, the present invention incorporates a programmer and anintegrator for enabling the output signals of particle detectionapparatus, such as disclosed in the forementioned US. Patent 3,259,842selectively to control the counting of particles of various sizes andplotting this information on chart paper.

As mentioned generally above, the invention described in US. Patent3,259,842 is provided with means to pro duce a window of variable upperand lower limits to control the size range of the signals passed to thecounting apparatus. The window is produced by means of two thresholdcircuits each establishing a potential level by means of suitablebiasing potentials controlled by potentiometers. The circuit constantsare chosen to enable the full dynamic range of the particles beingstudied to be achieved, so that said limits of the window can be variedselectively in increments along the entire range in order to give asfine or as coarse a determination of size distribution as desired.Obviously, any particle size can be chosen and only that informationused, if desired. Suitable calibration of the thresholds by dials orscales traversed by the potentiometer pointers is achieved readily.

It is important in many fields to know the relative distribution ofparticle sizes in a test sample. Formerly this required the successivemanual adjustment of the threshold potentiometers so that the operatorcould obtain -a count of the particles in each size range or grouping.The manual adjustment was subject to both error and considerable timedelay and since the particle range may change in certain fluids such asblood with the passage of time, the readings did not always reflect theactual condition of a fresh fluid sample.

In addition to the above, time was required for the tabulation andworking out of the plot or graph of the results. Another factorresponsible for error readily creeping into such determinations was theneed for an accurate timing interval for each trial.

It is one of the primary objects of this invention to provide means foreliminating the disadvantages attendant upon the use of said apparatusby manual methods which comprises programming structure which can beadjusted 3. automatically to plot information concerning the sizedistribution of particles of a given sample suspension.

Further objects of the invention are the provision of means enabling theautomatic selection of the timing interval during which each size rangeof particles is being scanned; the provision of means for selectingautomatically only predetermined size ranges of particles to be plotted;the provision of means for selecting automatically starting and stoppingranges for the plotting of a given distribution curve; the provision ofapparatus to register the total number of particles in any desired sizeranges. Further objects of the invention are concerned with theprovision of'novel switching and circuit apparatus to accomplish thegeneral functions desired of the apparatus including, meansforintegrating the pulses passed in any given interval in order to providea value representative of the said number for plotting purposes, andmeans of performing this function successively for a group ofdeterminations, and the like.

The foregoing and other objects of the invention will become apparent asthe description thereof evolves in connectionwith which, a preferredembodiment of the invention has been described in detail and illustratedin the accompanying drawings. It is contemplated that minor variationsin the size, arrangement, proportion and construction of the partsthereof may occur to the skilled artisan without departing from thescope or sacrificing any of the advantages of the invention.

In the drawings:

FIG. v1 is a block diagram of apparatus for automatically plottingparticle data which is constructed. in accordance with the invention,the same being shown associated with particle detecting and countingapparatus for controlling the. operation thereof for the purposes of theinvention.

FIGS. 2 and 2a are circuit diagrams, illustrating the details of theprogrammer shown in FIG. 1.

FIG. 3 is a circuit diagram of the integrator of FIG.

l; and

FIGS. 4 and 4a illustrate respective types of characteristic graphsprovidedby the apparatus.

Referring now to FIG. 1, there is illustrated a block designated 100representing the detecting orifice apparatus; a block designated 150representing the apparatus for controlling particle detection andcounting; a number of blocks respectively designated 310, 320, 330, 340and 350 within the broken line 300 and representing apparatus forintegrating the number of detected particles; a block designated 160representing any well known type of graph plotting apparatus; and ablock designated 200 representing programming apparatus forautomatically and selectively controlling the functions and operationsof the apparatus in the other blocks.

The detecting orifice apparatus 100 is known as a -stand usuallycomprises a pair of vessels, one having an aperture submerged in a testfluid contained in the other vessel and means for drawing the fluidthrough the aperture as described, for example, in the aforementionedvpatents. The fluid is a suspension of particles of various sizes whichare to be detected for counting and/ or sizing, and concerning whichinformation it is desired to, plot graphs.

The apparatus 150 for controlling particle detection and countingincludes means described in the aforementioned patent application forproviding an electrical current through the orifice and structure forexercising other control functions such as'initiating the passage of apredetermined volume of fluid through the orifice. This apparatus may betermed the detector although many additional functions are, or can beperformed thereby.

The detector apparatus 150 includes. circuitry for rejecting pulsesoccurring as a result of passage of particles which do not fall withinthe limits defined by the window above referred to. It also permits thepassage of thosev pulses which fall within the limits defined by saidwindow to a counter device all as described in theaforementioned US.Patent 3,259,842. The counter device may comprise any well known type ofcounting or registering arrangement for sequentially registering suchpulses such as, for example, glow counter tubes of the decade type whichindicate the count in successive tubes by the position of a glow atrespective electrodes.

Each .particle which passes through the aperture of the stand will varythe impedance to the flow of current through the aperture and suitableelectrodes for instance, in the fluid on opposite sides of the aperturecan detect this change in impedance and produce a signal, theamplitudeof which is related to the size of the particle. Thus, thenumberof particles which pass through the aperture will correspond tothe number of pulses produced, and the amplitudes of these pulseswillvary in accordance with the size of the respective particles. Thesephenomena enable the counting and sizing to be achieved. The detectorapparatus has a pair of threshold circuits each ofwhich is controlled bya-potentiometer whose purpose it is to define the limits of the, windowthrough which the desired sizes of pulses only are applied to thecounter apparatus. The potentiometers are shown in FIG. 2a at 130 and140. These limits may be varied as desired by adjusting saidpotentiometers to pass pulses within either narrower or larger sizeranges or in successive steps. The latter problem oftencreatesconsiderable difficulties since the potentiometersfor setting the upperand lower limits successively must be adjusted if particles withinsuccessive limits are to be counted and since'over a period of time thesample may change character so that the particles therein may varyeither from the standpoint of size or number. Thus, this creates one ofa number of received pulse to ,a charge pump represented by block,

340. .A clamp 330-serves to'limit the excursion of this pulse to apredetermined value so that; the charge pump 340 receives the samecharge for each pulse. The charge pump, 340feeds an integratingamplifier, indicated by block 350, which integrates the'received pulsesto control a recorder indicated by the block cbnnected by cable toamplifier 350. The integrating'arnplifier maybe of any well knowncommercially available type.

The recorder 160 may be of known construction comprising a motor fordriving a strip of chart or graph paper and an arm or stylus having arecording pen, for example. The recording pen may move along theordinate or Y'axis of the graph paper a distance corresponding to theamplitude of a signal applied thereto by the integrating amplifier 350,as the chart or graph paper is moved by the drive motor. The plotprovided by the pen therefore traverses an area of thepapercorresponding to the total particle count in any particular timeinterval over which measured. The maximum recorded movement of the penat the recorder 160 along one axis therefore records the maximum numberof received pulses within the particular time interval that theamplifier 350 is integrating and therefore for a respective size range.If a series of such records are made as indicated at c and d, forexample in FIG. 4, the maximum recorded position of each provides anindication of the relative distribution of particles of different sizes.Thus in FIG. 4a series of movements of the pen along the Y axis areillustrated. These represent plots .of the number of particles inrespective size ranges, while the envelope curve 2 fashioned permittingthe detection and counting sequence for particles passing through theaperture at stand 100* selectively and automatically to be controlled.The connecting cable 232 to the integrator 300 permits control of theintegrating amplifier in synchronism with the detector 150. The line 301connecting the integrator 30!) to the detector 150 transmits a pulse tothe linear amplifier 310 each time a pulse lying within the thresholdlimits or window is detccted. For each pulse transmitted to theamplifier 310 a pulse is also applied to the decade glow counter tubes295 and 296 shown in FIG. 2 so that they may provide simultaneously acount of the pulses passed through the window.

Referring to FIG. 2, the programmer 200 includes a switch S9 by means ofwhich suitable ones of the leads 101-121 are chosen to achieve thedesired control. Thus, the potentiometers 133 and 140 are disconnectedfrom their various potential supply leads and output leads and insteadthe resistors P1-Px are connected in their place to control thethreshold or window limits. In addition, the stop and start control andvarious reset leads controlled by switch S9 are arranged to be connectedto potentials supplied from the detector 150 for the purpose of insuringthat the same potential values are available throughout the system whereneeded. Further, the programmer has its own 110 volt supply indicated at299 and various rectified potentials are supplied therefrom foroperating certain relays and stepping switches at the programmer.

The programmer 200 has a timing motor TM which serves to provide asignal representative of a predetermined time interval and a switch TSfor counting those intervals. The time selection switch S1 permitsselection of a desired number of those intervals during which particlesof a particular size can be counted and a graph thereof plotted.

The switch M provides an arrangement for successively selectingresistors P1Px to set the lower and upper threshold limits of differentwindows at respective values so that the number of particles passed byeach window may be gauged. Switch M at its level A also provides anindication as to which of the windows or particle size ranges is beinggauged. Switch S2 permits a selection to be made as to the particle sizegroup or window at which the graphing or counting is initiated.

The programmer 200, in addition, has a switch PB2 for stopping allfunctions; a start switch PBl which initiates operation of theprogrammer and a record switch PBS by means of which its recordingfunctions are initiated. The programmer also has the switch S4 whichpermits the count registered at the glow counter tubes to be retainedfor a desired interval while the graphing or recording operationcontinues so that the operator or attendant may know the precise countwhich has been registered for a particular graph. It will be understoodof course that once the apparatus is calibrated and the graph papermarked accordingly, the count may also be simply read off the paper. Theswitch PB6 permits the number of particles in either odd or. evennumbered windows or particle size ranges to be counted by the countertubes when switch S4 is operated from the position shown in FIG. 2 to analternate position. The switch S8 permits resetting of the glow countertubes.

In brief, the programmer switch S9 is operated when it is desired tohave the programmer 200' control the apparatus for enabling the recorder160 to plot a graph of particles passing through one or more of thewindows. The start and record push buttons PB1 and PBS respectively arethen successively pressed to initiate the opera tion of the programmer200. These push buttons are momentarily depressed for causing theenergization of the relays 2111' and 220 in succession through suitableconnections which are readily seen in the diagram of FIG. 2.

The relay 220 closes contacts which provides a connection for the timingmotor TM by way of the connecting leads d and c to the power source 299.Rotation of the timing mot-or TM and its coupled cam TC-1 closes the camcontact switch TM1 at timed intervals, for example in the structureillustrated, every four seconds. The closing of the contacts TM1energizes the relay driving the stepping switch TS, causing the armthereof to be stepped to the next position relative to that which it hadbefore energization. The position of the arm of switch S1 will determinewhen the wipers 'of the stepping switch TS are released to return totheir initial position.

Switch M is operated simultaneously with the release of the switch TSand it will select the threshold limits of window within which thepulses from the detector 150 are to be counted and plotted. Aspreviously mentioned, the count of the particles is registered on thecounting indicator coupled to the detector structure 150 and at the sametime pulses corresponding to the particles are passed to the integrator300 to control the recorder.

The switch S1 may be set manually to any one of a number of positionsfor selecting the scanning time period for each window. Switch TS isstepped once for each four-second interval until it reaches the positionselected by S1. When the wiper arm of TS has advanced to the positionchosen by the switch setting of S1, the switch M is stepped. In elfect,therefore, each window will be scanned for a time interval from 4 to 40seconds, in foursecond increments, as determined by the setting of S1.

Operation of the recorder 160 for plotting or graphing the relativedistribution of particles in dilferent size ranges is initiated undercontrol of the programmer 200 by moving switch S9 to the positionthereof shown in FIGS. 2 and 2a. Switch S9 is a gang switch havinglevels A-J, the levels A-D of which are shown in FIG. 2 and levels E-]are shown in FIG. 2a. This ganged connection is indicated by the brokenline x. Movement of switch S9 to the illustrated position thereofdisconnects the stand from control of detector 150 and places both thestand 100 and detector 150 under control of the programmer 200. Thepotentiometers and for establishing the lower and upper levels of thewindows are now disconnected at levels EJ of switch S9 and therespective resistors P1-Px are connected in their place. The dottedconnections from various levels of switch S9 are provided merely toindicate specific apparatus such as potentiom eters 130 and 140 andvarious sources of potential are at the detector 150. These areillustrated primarily to enable easier visualization of the manner inwhich the programmer 200 is interconnected with the detector so as toexercise various controls, which are ordinarily exercised by thedetector. It will also be understood that certain auxiliary functionsperformed at the programmer 200, which are not necessary to theunderstanding of the functioning of the programmer and detector 150 havebeen eliminated to avoid an unnecessarily lengthy and complexdescription.

Switch LS is closed to supply power from the 110 volt source 299 by wayof the cable 199 to the motor (not shown) of the recorder whichinitiates movement of the record paper. Switches S1 and S2 are manuallyset to a desired position as previously explained. Switch S1 isoperative to select the desired timing interval during which therespective windows are scanned. Switch SZ-is operative to enable switchM to select any initial, or starting, window among the group followingthe momentary operation of switch PBS. This sequence will besubsequently described.

The start switch or button PB1 is operative to connect the AC relay 210across the power supply 299. Relay 210 energizes and locks operated overcontacts 211 and 241 and through the contacts B of the manual stopswitch PB2. The contacts of the start button PBl are now shunted so thatits release on removal of the operating pressure thereon does not affectrelay 210. Relay 210' removes ground from normally operated relay 230 atcontacts 215 and that relay restores to open contacts 231. With contacts231 open, the short extended by means of cable 232 to the integratingcapacitor 356 in the integrator 300 is removed and the amplifier 350 nowfunctions to integrate the total number of pulses detected as a resultof detectable particles passing through the orifice in the stand 100. Itwill be understood, however, that pulses may.

be blocked from the integrator 300 in any wellknown manner until theswitch TS is sent through one time cycle, or the. graph resultingfrom'particles received before switch TS completes one cycle, may beignored. Either of these latter procedures is available for the reasonthat the first window or threshold limits are not determined, untilswitch TS completes one cycle. At contacts 214, relay 210 prepares acircuit to relays 230, 250 and 270 in shunt from the level A wiper ofthe time selection switch S1. At contacts 212 a circuit is completed byrelay 210 for applying the potential onlead 108 to lead 103 forinitiating current flow through the detecting orifice or aperture atstand 100. At contacts 213 'relay210 connects the potential on lead 108through contacts 271 and 252 to lead 107 to initiate particle detectionat detector 150. These contacts 213 are thus similar to the meteringcontacts such as utilized in connection withcertain apparatus associatedwith the orifice and which responds to the passage of fluid through theorifice to permit particle detection. Other contacts such as 212 or 213may also be closed either during or after operation of button FBI toinitiate operation of the valve or pump (not shown) for drawing fluidthrough the orifice at stand 100; however, this may also be accomplishedover leads 103-or 107 in any well known manner.-

The operator now operates the record button PB3 to plied by way of leadb to one spring of both contacts TM1 and273 and also to the level A andB wipers of the time count or step switch TS.

The timing motor TM closes contacts TM1, after a four-second interval,to forward ground from contacts 211, past contacts TM1 to the steppingmagnet of switch TS. This switch is arranged with a direct drive so thatthe magnet wipers of levels A and B of switch TStherefore move to theirfirst bank contact or position. This connects ground on lead b to thefirst bankcontact on each of the levels A and B ofswitch TS. Since thesebank contacts are connected to respective bank contacts of levels A andB of switch S1, ground is extended to the first bank contact steps itsassociated wipers on energization. The

.40 at four-second intervals. At contacts 221 ground is ap-' of levels Aand B of switch S1 if switch S1 is set to its first position.

switch M is in its home position. In this position its level C and Dwipers are both connected to the level H wiper of switch S9 and aretherefore at the reference potential supplied by means of lead 117 fromthe detector 150. The level D wiper extends this potential over level Iof switch S9 and lead 121 to control the lower threshold limit, whilethe level C wiper now extends the same potential past they switch P8 tocontrol the upper threshold limit by means of level P of switch S9 andlead 113. The threshold limits at this position may be balanced by theadjustment of suitable resistors which are not shown. It will be notedthat although the level D wiper of switch M is denoted as moving in adirectionopposite that of the other wipers. This is done only to enablethe various connections between the bank contacts and resistors PI-Px tobe simplified, it being understood that all of the wipers of switch Mnormally move in the same direction.

The referencepotential at the level H wiper of switch S9 is alsoconnected through resistors Pl-Px. Resistor Px is connected by means ofresistors R31 and R30 to another reference potential supplied from thedetector 150 to lead and level I of switch S9, and therefore a voltagedrop is provided across each of the respective resistors, Pl-Px. SwitchM is arranged to sequentially connect the respective wipers C and D toalternate ends of successive resistors Pl-Px, as the switch is steppedthrough successivepositions. Each of the wipers will therefore supplyrespective threshold limit potentials to the detector 150 for settingthe respective upper and lower thresholds in contiguous steps as switchM is stepped through its successive positions.

' The height of the window is determined by the potential differencebetween the upper and lower threshold limits or potentials and thesedepend on the voltage drop across the respective resistors Pl-Px.Resistors Pl-Px can therefore be arranged to provide either equal ordiffering voltage drops depending on desiredwind'ow heights ordifferences between threshold limits. Thus both successive and equalcontiguous ranges of particle size are enabled to be detected at thedetector 150. Resistor R30 is normally adjusted to set the maximum upperthreshold I mally supplied by adjustment of the potentiometer v at thedetector 150. Thus with both the minimum lower andmaximum upperthreshold limits set at respective values corresponding to thosesupplied by adjustment of potentiometers and 130 respectively, theresistors Pl-Px supply respective upper and lower threshold limits lyingwithin the range provided by the detector 150.

If switch S1 had been set to its'first back contact indicating that afour-second interval is chosen for scanning each window, the ground tactfrom the levelA wiper of switch TS is forwarded from the level A wiperof switch S1 and lead A, past contacts 254, 214 and 224 to energizerelays 250, 230 and 270. Relay 230 is energized directly from contacts214 and relay 250, of course, energizes directly from the groundat thelevel A'wiper of switch S1. Relay 250 is slow to operate and slow torelease and after it operates, it opens the operating circuits forrelays 230 and 270 at contacts 254; however, those relays have alreadyenergized at that time.

Relay 230 at contacts 231 shorts the integrating capacitor 356 by meansof cable 232 so that it is reset to its initial condition. The pen orstylus of the recorder therefore starts to return to its zero line asthe output of the amplifier 350 returns'to zero volts. Relay 270 extendsthe potential from lead 108, past contacts 253 to provide a stopbias byway of lead 109 to the detector 150. This now terminates operation ofthe detector in much the same manner as done with stop contactsdescribed in previous particle counters so that the number of particlesmay be related to a desired volume of fluid flow through an orifice.Thus by starting andstopping the detector 150 at predetermined timeintervals during which the fluid is drawn through the aperture ororifice at stand 100 at a predetermined rate the number of particles isgauged against a particular or desired volume of fluid.

At contacts 271, relay 270 disconnects lead 108 from 107 extended to thefirst bank con- 2 The level B wiper of switch TS in the meantime extendsthe ground from contacts 221, past the level B wiper of switch S1 andthe off normal springs ON of switch TS to energize the release magnetRLS of switch TS. Magnet RLS now sends the wipers of switch TS to theirhome position to open the oit normal spring ON. The operate period ofmagnet RLS may of course be controlled in any one of a number of wellknown manners to insure that the wipers reach home, but which form nopart of the present invention and are therefore not shown or discussed.

At contacts 252 and 253 relay 250 opens both the start and stop circuitsextending over leads 107 and 109 respectively. At contacts 251 relay 250connects the capacitor C2 to the capacitor C1. Capacitor C1 is normallycharged to a high positive value through the bridge circuit comprisingresistors R1, R2, R3 and R4 connected between a positive potential onlead 106 and the potential on lead 108. Capacitor C2 on the other handis at a value substantially corresponding to the potential on lead 108as it is charged through resistor R5. When it is connected to capacitorC1 responsive to the closure of contacts 251, capacitor C1 transmits amomentary negative reset pulse to lead 102, as it swings toward thepotential of capacitor C2. The reset pulse on lead 102 enables the cyclefor drawing fluid through the aperture at stand 100 to be repeated. Atcontacts 254 the circuits to relays 230 and 270 are restored.

When relay 270 is restored, the circuit to the magnet of switch M isopened. The magnet is de-energized to step the wipers of levels A, B, Cand D to their next contact. At contacts 271 the start circuit over lead107 is again prepared and at contacts 272 the stop circuit over lead 109opened at another point. Relay 230 opens the integrating capacitor 356short at contacts 231. As the wipers of switch TS step toward home, thecircuit to relay 250 is opened, and it restores, after a period of timeso that the start bias for detector 150 is now reapplied over contacts252. At contacts 251 capacitor C2 is disconnected from capacitor C1 andthe charge on each returns to its original value.

The coil of relay 290 de-energizes on release of relay 270, but first itcloses contacts 291 to apply the potential from lead 108 to the glowcounter tube bias lead 101 for no purpose unless switch S4 is operatedfrom the position in which it is shown. Switch S4 level B is normallymaintaining a bias potential on lead 101 to the glow counter tubes. Thebias permits the glow counter tubes to sequentially record or total thenumber of detected particles. At contacts 292 relay 290 prepares a resetcircuit to the glow counter tubes over lead 105, but this remainsincomplete, as switch S4 level A is unoperated. The contacts of relay290 will now remain in the position to which they were operated, untilthe next energization of the relay 290, at which time the contacts arereversed.

The count provided at the glow counter tubes during the first step ofswitch TS and indicated by the graph line 1 in FIG. 4 may serve nopurpose, as the threshold levels may be set so low as to permit micro ormacro particles or background noise to be detected and recorded .by therecorder 160.

It may be desirable to thereafter maintain or provide a record of thetotal number of particles passed through one or more windows in order tocalibrate the graph paper, for example. The operator notes the return ofthe recording pen to the zero line during operation of relay 230. Thisreturn occurs as a result of the short on capacitor 356. He thenmomentarily operates the reset switch S8. Level B of the switch S8servesthe same purpose as contacts 251 by causing the transmission of anegative reset pulse over lead 102 as explained. The level A wiper ofswitch S8 connects the glow tube counter reset lead 105 from level C ofswitch S9 to the lead 102 and capacitor C1 so that it likewise receivesa reset pulse. The pulse on lead 'resets the glow counter tubes so thatthey may initiate the particle count from their zero positions.

In its first position, the level A wiper of switch M extends ground tothe first neon tube NE1 for firing that tube. This indicates to theoperator that the particles in a size range corresponding to the firstwindow are now being plotted or graphed. At level B of switch M therelay 280 is connected to the first bank contact. This relay iscontrolled in accordance with the setting of switch S2 as will beexplained.

It will be noted that the respective opposite ends of series connectedresistors P1, P2-Px are connected to corresponding ones of the bankcontacts 1-25 of respective levels C and D of switch M. The oppositeends of the resistors therefore provide a voltage of ditierent valve atthe corresponding bank contacts of the two levels and that differencedetermines the height of the window between the lower and upperthreshold limits. As the respective wipers are moved successively pasttheir bank contacts, each will transmit the respective voltage thereatto the detector for setting the respective threshold limits. As theupper and lower limits are moved by a fixed amount on each step ofwipers C and D, the window or size range will be proportionatelyadjusted to permit particles from fine to coarse grades to besuccessively registered. Thus the wiper of level C applies the potentialit derives to level F of switch S9 and lead 113 to set the upperthreshold limit at the detector 150 at one limit of particle acceptance,while the level D wiper transmits its potential to level I of switch S9to set the lower threshold limit of particle acceptance at the dectector150 in successive contiguous steps as the wipers are moved past theirbank contacts. It will be appreciated that the diiference between theupper and lower threshold limits at each step depend on the chosenvalues for resistors Pl-Px. If desired, therefore, the differencebetween the threshold limits at each step may be either equal or not asdesired. Further, the respective threshold limits need not becontiguous, as by inserting resistors at desired positions betweenPl-Px, certain size ranges may be skipped or omitted.

With the upper and lower threshold levels now set by the resistancevalues connected to the wipers of levels C and D of switch M, thedetector apparatus 150 responds to particles passing through theaperture at stand 100 that generate pulses whose characteristics aredefined by these limits. The detector 150 provides a pulse individual toeach successive particles and these pulses are fed in succession overline 301 to the linear amplifier 310 and also to the glow tube countersfor advancing the count registered thereby.

Referring now to FIG. 3, it will be seen that the line 301 extends tothe grid of amplifier tube 302 in the linear amplifier 310. With apositive pulse, representing a particle passing through the orifice atstand 100, appearing on line 301, the plate circuit of tube 302 swingsnegative and a corresponding negative pulse is transmitted through thecapacitor 303 to the grid of tube 304. The plate circuit of tube 304therefore swings positive and a positive pulse is transmitted throughthe capacitor 305 to the diode D1. The positive going portion of thispulse is transmitted through the diode D1 to the grid of tube 324 in theunivibrator 320. Tube 322 of the univibrator is normally conducting dueto the bias arrangement provided for the tube; however, when the grid oftube 324 swings positive, the plate circuit of that tube 324- swingsnegative and a corresponding negative pulse is transmitted through thecapacitor 323 to the grid of tube 322 to cut that tube 322 off.

The clamp tube 335 is normally connected between the high potentialsupply for the plate circuit of normally nonconductive tube 324 andground through the resistor R90. The clamp tube 335 is a gas tube havinga constant voltage drop characteristic and is normally fired at about 85volts so that it is conductive and the diode D2 reverse biased. Thenegative swing in the plate circuit of tube 324 is transmitted throughthe resistor R85 to charge capacitor 337. The diode D2 becomes unblockedwhen the plate circuit of tube 324 becomes sufficiently negative anddiode D2 passes current through the tube 335. This limits the negativecharge value on capacitor 337, thereby clamping this capacitoraccordingly.

As capacitor 337 swings negative, the diode .345 begins to conduct andits cathode therefore swings slightly positive. After the termination ofthe univibrator pulse, capacitor 337', which has charged through diode345, now discharges through diode D3 and the resistor R94 to theintegrating amplifier 355.

The output of the amplifier 355 varies accordingly and is applied overthe cable 165 for moving the recorder pen or stylus across the chartpaper along theordinate axis. Each successive input pulse from capacitor337 causes the charge on integrating capacitor 356 to increase, as wellas the output voltage of 355 so that the recording pen moves toansuccessively higher position along the y or ordinate axis of the graphpaper with each successive pulse. Since the amplifier 355 is a high gainamplifier and the capacitor 356 is considerably larger than capacitor337 the output voltage of amplifier 355 is retained between successivepulses.

As the diode D1 is blocked after the positive swing in the plate circuitof tube 304, the grid circuit of tube 324 returns towards its normalvalue and with the bias arrangement provided for tube 322, that tube 322again initiates conduction. As the plate circuit of tube 322 swingsnegative, that swing is transmitted to the grid circuit of the 324 tocut that tube otf. With the plate circuit of tube 324 swinging positive,the diode D2,is again blocked,-and capacitor 337 returns to normal.

This train of events will be repeated with each succeeding pulseappearing on lead 301; however, on each'succeeding pulse applied throughthe diode D3 the amplifier 355 is raised due to the fact that theamplifier 355 and the capacitor 356 have a large capacitative effect ascompared to the capacitor 337. Thus each received pulse willprogressively increase the output of amplifier 355 along a substantiallylinear curve provided by the characteristics of amplifier 355 and therecording pen will move accordingly. The capacitor 356 and the amplifier355 therefore serve to integrate the received pulses, and the number ofpulses received will be reflected by the output output of level of theamplifier 355. The line traced by the recording 7 pen on the graph paperin its maximum position along the ordinate axis, reflects the totalnumber of particles in a particular window or size range.

At the end of the particular scanning or time interval determined by thesetting of switch S1, relay 230 is operated as explained to connect theleads of cable 232 from both sides of capacitor 356 together and thecapacitor 356 returns to its initial condition. A succeeding plot orcurve representative of the number of particles in the next window maythereafter be plotted by the recorder 160 after the recording penreturns to its initial or zero position responsive to the discharge ofcapacitor 356 for resetting the output of amplifier 350.

It will be recalled that the timing motor is closing contacts TM1 atfour-second intervals. The switch TS may thus he stepped home after thefirst four-second interval if switch S1 is set on its first bankcontact. Therefore, assuming switch S1 is on its first position and thatswitch TS is stepped to its first bank contact responsive to the closureof contacts TM1, that switch TS will thereafter be stepped home in themanner explained. The stop and start bias leads-107 and 109 togetherwith the reset lead 102 are again controlled as explained.

Relay 270 operates as before explained to reoperate the motor magnet ofswitch M and that switch steps to its second position. In this positionresistor P2 is now connected in the aforedescribed circuit to thethreshold setting leads 113 and 121 so that additional increments arenow old at a new level above the lower level. The number of particleswill again be registered by the glow counter tubes and added to thetotal registered previously. They will also be integrated by theintegrator 300 to move the recording pen for plotting a curverepresentative of the number of particles between the two secondthreshold limits. Neon tube NE2 is now lighted as the M switch level Ais in its second position. With the switches, set, as described,-thisprocedure for moving the recording arm and totalling the particles byregistration at the glow counter tube is repeatedfor each ofthe 25ditferent threshold limits or windows to move the recording pen atrecorder 160 along a ditferent ordinate or Y axis for each window asshown in FIG. 4. The distance moved along ordinate Y axis corresponds ofcourse to the number of particles present in the fluid sample of a sizerange corresponding to particular threshold levels and successivelyplotted along the X or time-axis. Thus the switch M is stepped in themanner explained through each of its positions 1 to 25 for setting thedifferent upper and lower threshold limits and a different graphprovided for the particles lying within each different size range, asexplained. The graphs may now be compared to secure information as tothe distribution in the fluid sample of particles of dififerent sizes asshown by the curve e in FIG. 4.

After a graph has been made corresponding to the number of particlesdetected within the size range set by the threshold levels provided byswitch M in its 25th position theswitch M is stepped to its homeposition. Thus the timing motor contacts TM1 close after switch M hasbeen stepped to position.25 and they restore switch TS While relay 270is operated and restored as explained.

The motor magnet of switch M is also energized and deenergized asexplained and it steps the wipers of switch M to their home position.The oif normal springs 0N1 close to ground lead g. This causes thecapacitor C9 to- Contacts 241 on openingv restore relays210 and 220.

Contacts 211 therefore opento terminate operation of the motor TM and nofurther operation of switch TS or M can thereafter occur, unless theoperator again operates buttons FBI and PB3 to repeat the cycle. It willbe noted that the 25 different size ranges are registered insubstantially seconds with switch S1 set in its first position and thateach time interval is an accurate duplicate of the others.

In the meantime the glow counter tubes are operated successively by eachpulse generated by the particles to record a count corresponding to thetotal number of particles passing through the aperture at stand 100andwithin the size range determined by the threshold limits.

In summary the buttons FBI and PB3 are momentarily operated toenergizerelays 210 and 220m succession. Relay 220 energizes the timing motor TMwhich operates detector and the integrator 300 controls the recorder toprovide a graph corresponding to the number of particles.

Switch S1 may beset to any one of ten positions, to

control the number of steps taken by'switch TS corre spondingly beforestepping switch M. Since switch TS is 13 stepped once every fourseconds, the time interval between steps of switch M may be controlledfor a desired multiple of four seconds and therefore the length of timefor scanning each window is set in accordance with the position ofswitch S1.

Operation of switch S4 controls counting by the glow counter tubes toenable them to total the number of particles in every other or alternateposition of switch M and hold the count for a time interval. The timeinterval during which the number or count is held by the glow countertubes is sufiicient to permit the preceding size range to be recorded.The recorded number may be placed on the chart paper adjacent theparticular graph. Thus operation of switch S4 from the position shown inFIG. 2 disconnects lead 101 from lead 108 at level B and places the glowcounter tube bias lead 101 under control of contacts 291 of the ratchetrelay 290. At level A of switch S4 the glow counter tube reset lead 105is placed under control of contacts 292 of relay 290. Since the ratchetrelay 290 holds contacts 291 and 292 either open or closed forsuccessive steps of switch M, the contacts 292 will be closed onalternate steps of switch M. It will also be noted that relay 290 isoperated coincidentally with the magnet of switch M so that contacts 291and 292 close just before switch M takes the corresponding step. Thereset pulse applied through capacitor C1 at the end of each step ofswitch M will be applied past level A of switch S4 and contacts 292 toreset the glow counter tubes to zero just before switch M takes the stepduring which contacts 292 are held closed. At the beginning of eachalternate cycle or step during which contacts 291 are closed, the biasfor the glow counter tubes is applied to lead 101 to enable the glowcounter tubes to count or record the total number of particles duringthe corresponding step of switch M.

Therefore when switch S4 is operated, an initial reset pulse is appliedto reset the glow counter tubes as soon as relay 290 closes its contacts292 and since bias is then applied to the counter tubes at contacts 291,the counter tubes subsequently record the number of particles lyingwithin the threshold limits next selected by switch M.

Since relay 270 subsequently operates relay 290 before relay 250 canclose contacts 251 while switch M is in the next selected position,relay 290 opens contacts 291 and 292 before the reset pulse can beapplied at lead 105. Switch M therefore takes a succeeding step toanother position and relay 29,0 holds contacts 291 and 292 open duringthat step and while switch M is in the other position. The count istherefore retained by the glow counter tubes until the followingoperation of relay 290. Thus the glow counter tubes retain the recordedcount for an interval corresponding to a complete scanning intervalbetween steps of switch M. During this interval the operator may markthe count on the graph paper.

The operator may choose whether the counts retained by the counter tubescorrespond to odd or even numbered windows. Thus by noting whether lamp295 or 296 is lighted he knows the position of the contacts 291 and 292for the even or odd windows. He simply operates switch PB6 momentarily,after S4, to operate relay 290 and change the sequence so that contacts291 and 292 are closed in a sequence corresponding to either the odd oreven numbered positions of switch M as noted by lamp NE1 etc. Recordingthe counts registered by the glow counter tubes on the graph paper alonga respective line corresponding to the maximum position on the Y axis ofthe respective graphs permits the count for each subsequent graph to beread directly off the graph paper by comparison.

If the operator did not wish to include a certain count corresponding toa size range determined by for example the first window, he momentarilyoperates the switch S8. He may of course note the window or particlesize range being graphed by observing whichof the lamps NE1- NE25 arelighted. At level B of switch S8 a reset pulse is generated throughcapacitor C1 and extended through level A of switch S9 to lead to resetthe counter tubes and other apparatus as already explained. Theoperation will thereafter proceed as described.

If the operator decides that the graphing should begin at a particularsize range, switch S2 is set at a position corresponding that thatrange. The operator also operates the pushbutton PB4 momentarily toapply ground to the relay 280 which locks operated through its contacts282. At contacts 281, relay 280 applies grounds to the self-interruptingcontacts of the motor magnet of switch M and the switch wipers are nowstepped selfinteruptedly, until its level B wiper is associated with thebank contact corresponding to that at which switch S2 has been set. Atthat time battery is extended from the wiper of switch S2 to the wiperof level B of switch M and relay 270 restores due to the shunting effecton the relay coil. -It will be noted that switch M is thus steppedindependently of switches TS and S1. Contacts 282 open as do contacts281 on release of relay 280.

Opening of contacts 281 thereafter prevents selfinterrupted stepping ofthe motor-magnet of switch M and the recorder 160 may then be controlledas already described. That is, to control the recorder, switches FBI andPB3 are operated to step the timing switch TS and the switch M undercontrol of the timing motor TM as explained.

If it is desired to stop the recording or graphing operation after anyparticular position is reached, the neon tube corresponding to thatposition is observed and when lighted, the stop button PB2 ismomentarily operated. The stop button PB2 opens the holding circuit forrelays 210 and 220 at level B so that both relays restore. Level A ofbutton PB2 extends ground by way of lead 7 to the release magnet RLS ofswitch TS and that switch steps home. At button PBS the operatorconnects ground from the operated 011 normal springs 0N2 to the motormagnet of switch M to step the switch home self-interruptedly. 011normal springs 0N2 open in the home position of the switch M to open thehoming circuit. 01f normal springs 0N1 close in the home position topulse relay 240 and that relay restores relays 210 and 220. Since thetiming motor TM is now de-energized, no further operations will occur.

In certain instances it may be desirable to graph or record particlesabove a certain size. Switch P8 shown in FIG. 2a is then operated fromthe position shown to disconnect wiper C from level F of switch S9 andconnect one end of resistor Px to level F. The potential at the junctureof resistors Px and R31 will now be extended to the detector to set theupper threshold limit at a maximum value regardless of the position ofswitch M. The lower threshold limit, however, will be progressivelyadvanced as switch M moves through its respective positions. The resultis to continually decrease the window width towards the upper limit asswitch M is moved to its respective positions. Usually the total numberof particles above a particular size will decrease as the lower limit ismoved upwards and the graphs of the number of particles in thecontinually narrowing Windows are illustrated in FIG. 4a. Thus in thatFIG. 4a the graph of the first window is indicated at the O and willprovide an indication of the total number of particles from the lower tothe upper threshold limits. As the window is progressively narrowed thenumber of particles above a particular size determined by the respectivelower thresholds decreases as shown at P and Z for example and therelative distribution of the particles above respective sizes indicatedby the envelope curve R.

When it is desired to discontinue use of the programmer 200, switch S9is switched from the position shown. This connects the counter bias lead101 directly to lead 108 so that lead 101 is under control of thedetector apparatus 150. At levels B and C of switch S9 the stop-startreset lead 102 and the glow counter reset lead 105 are placed undercontrol of the detector 150. At level D the 15 means for furnishing thestart bias from the programmer,200 to lead 107 is disconnectedso thatthe start bias may be furnished under control of the metering contactsat stand 100.

At level E of switch S9 one potential is connected to lead 110 extendingtothe detector 150 and the potentiometer 130 thereat. The level F ofswitch S9 connects the potentiometer arm over lead 112 to lead 113 forsetting the upper level of one window or threshold limit and at level Gof switch S9 the other end of the potentiometer 130 is connectedoverlead 115 to another potential. Similar connections are provided atlevels H, I and J of switch S9 for the lower level of the window orthreshold limit. Thus at level. H, a particular potential is connectedfrom lead 117 'to lead 116 and the potentiometer 140 and at level Ianother potential is connected from lead 120 to lead 119 and the otherside of the potentiometer 140. At level I the armvof potentiometer 140is connected from lead 118 to lead 121 forsetting the value of the lowerthreshold limit or window. The upper and lower threshold limits aretherefore placed under control of the respective arms of potentiometers130 and 140 and the size. of the windowset in accordance with thedifferent adjustments between the arms of potentiometers 130 and 140.

At this time another aspect of the invention will be mentioned in thatits concepts and broad. objectives may be accomplished by utilizingmeans other than a stepping switch such as. M. Thus instead of steppingthe switchM at selectedintervals, a motor (not shown) may beset inoperation at the initiation of the plotting sequence. It:

may progressively operate a pair of rheostat arms, for example, in anywell known manner to setthe threshold limits progressively and without,for example, shorting capacitor 356. This will result ina continuousdistribu-- tion curve of particle size, for example, as a function ofthe progressively changing limits. It is believed that the arrangementof such structure is obvious in view of the foregoing and that toillustrate the same would needlessly complicate the specification.

It is believed that this invention, its mode of construction andassembly, and many of its advantages should be readily understood fromthe foregoing without further description and it should also be manifestthat while a preferred embodiment of the invention has been shown anddescribed for illustrative purposes, the specific details arenevertheless capable as defined in the appended claims.

What is claimed and desired to be secured by Letters Patent of theUnited States is:

1. A particle distribution plotting apparatus comprising:

particle detecting orifice means providing a signal for each detectedparticle, each signal having a parameter which is a function of the sizeof each respectively detected particle, particle detectioncontrol'means' coupled to said particle detecting orifice means andreceiving eaohsaid signal, and said detection control means passing froman output thereof only signals representing particles within apredetermined size range, programming means coupled to said particledetection control means and regulating said size range, integrator meanscoupled to the output of said particle detection control means andreceivingeach of the signals passed therefrom, said integrator meansproducing an output which incrementally increases in magnitudeproportional to the number of signals received thereby, and graphicrecording means coupled to said programming means and beingoperationally controlled therefrom and also coupled to said integratormeans and receiving and graphing the output therefrom. 2. Apparatus asdefined in claim 1, wherein said integrator means comprises:

a charge pump. responsive to each of the signals re.

ceived by said integrator means, and

an integrating amplifier coupled to and progressively energized by saidcharge pump, the'output of said integrating amplifier being theoutput ofsaid integrator means, which is coupled to said recorder.

3. Apparatus as defined in claim 2, wherein said integrator meansfurther comprises:

a lineara-mplifier, a univibrator, and a voltage clamp serially coupledbetween said particle detection control means and said charge pump,saidvoltage clamp limiting the response ofthe charge pump to each ofsaid signals.

4. Apparatus as defined in claim 2 wherein, said charge pump and saidintegrating amplifier each comprises:

a capacitor, the capacitor of said integrating amplifier being seriallycoupledto and having a storage capacity considerably larger thanthe-capacitor of said charge pump. 5. Apparatus as defined in claim 4wherein, said programming means comprises:

relay means coupled acrossthe capacitor of said integrating amplifier,said relay means being periodically energized and providing a dischargepath for said capacitor and thereby resetting said integrator means.

6. Apparatus as defined in claim 1 wherein, said pro- 7 gramming meanscomprises:

means determining said size range to lie between a pair of predeterminedlimits. 7. Apparatus as defined in claim 6 wherein, said size rangedetermining means comprises:

electrically interconnected structure defining a plurality of pairs ofpredetermined limits corresponding to a plurality of different sizeranges. 8. Apparatus as defined in claim 7 wherein, said programmingmeans further comprises:

selecting meanscoupled to said size range determining means and at anyone time selecting a predetermined pair of said limits. 9. Apparatus asdefined in claim 8 wherein said se-. lecting means comprises:

successively advanceable switching means. 10. Apparatus asdefinedinclaim 9 wherein, said programming means further comprises:

a first range control means coupled to said successively advanceableswitching means and advancing it to a.

9 wherein, said pro- 12. Apparatus as defined in claim 7 wherein, saidelec-.

trically interconnected structure comprises:

impedance means having a plurality of spaced taps defining therebetweenaplurality of impedance differences'determinative of said plurality ofpairs of predetermined limits. 13. Apparatus as defined in claim 12wherein,,said size range determining means comprises:

multipositional switching means having first and second electricallyganged levels, each position within each level being connected to adifferent one of said, taps, the similar positions of both levelssimultaneously coupled to different taps defining any one of said pairsof limits, and, said programming means further comprises selectiveenergizing means coupled to said multipositional switching means for thepositioning thereof.

14. Apparatus as defined in claim 13 wherein, said programming meansfurther comprises:

limit fixing means selectively connectable to one of said levels andinhibiting the limit thereof from being changed by said selectiveenergizing means.

15. Apparatus as defined in claim 13 wherein, said multipositionalswitching means further comprises:

a third ganged level,

each position of said third level having means indicating the positionalstatus of said switching means and therefore the corresponding sizerange.

16. Apparatus as defined in claim 1 wherein, said programming means iscoupled to said integrator means and comprises:

means automatically and successively selecting a plurality of sizeranges,

means coupled to said graphic recording means initiating its operationupon selection of each of said size ranges and, via said integratormeans, resetting said recording means to a base line prior to selectionof the next size range, and

means coupled to said particle detecting orifice means,

said particle detection control means, and said integrator meansinitiating their operation, terminating their operation prior to theselection of each size range and after the selection of all size ranges,and restarting their operation after selection of each next size range,

whereby said recording means provides discrete graphs for each particlesize range, each discrete graph functionally related to the number ofdetected particles within each size range.

17. Apparatus as defined in claim 16 further comprising:

counting means coupled to said particle detector control means and saidprogramming means and providing a progressive visual indication of thenumber of particles within the selected size range being detected.

18. Apparatus as defined in claim 17 wherein, said counting meanscomprises:

a pair of counters, and

said programming means further comprises, means alternately energizingeach of said counters during successively selected size ranges, suchthat during detection of particles of any particular size range only oneof said counters is energized,

means retaining the visually presented count in one counter while theother counter is being energized, and

means resetting said one counter prior to its next energization.

19. Apparatus as defined in claim 1 wherein, said programming meanscomprises:

means regulating the time during which particles within a predeterminedsize range are being detected and their number graphically recorded.

29. Apparatus as defined in claim 19, wherein, said time regulatingmeans comprises:

incrementally advanceable means, and

timed energizing means coupled to said incrementally advanceable meansfor advancing it.

mined time interval, and

said time regulating means further comprising motive means coupled tosaid timed energizing means and providing cyclic movement thereto.

22. Apparatus as defined in claim 20 wherein, said incrementallyadvanceable means comprises:

presettable time control means determining the number of increments saidadvanceable means is advanced during the detection of particles within apredetermined size range, and

said time regulating means further comprises means resetting saidincrementally advanceable means after it has advanced said number ofincrements.

23. Control means in a recording instrument to graph in succession,curves representing respective numbers ofparticles of diiterent sizeranges detected by apparatus in which the particles are passed throughan orifice for varying a current through the orifice in accordance withthe particle size to permit current variations of less than a desiredamplitude to be rejected and current variations greater than anotherdesired amplitude to also be rejected and those current variations lyingbetween the two am plitudes to be registered, said control means,comprising; a switch, means connected to said switch for setting bothsaid desired amplitudes at respective ones of a plurality of differentvalues, and means for successively operating said switch to successivelyset said amplitudes at different values whereby said recordinginstrument is controlled in accordance with the current variationsrepresenting successive particle size ranges to provide said curves.

24. In the arrangement claimed in claim 23, means selectively operatingsaid amplitude setting means for controlling said recording instrumentin accordance with current variations representing any desired particlesize range only.

25. Apparatus for recording a series of graphs each individual toparticles of one of a plurality of respective size ranges whichcomprises, particle detecting apparatus which provides only one signalfor each detected particle, said one signal having a characteristiccorresponding to the size of its respective particle, means forselecting signals having a range of said characteristic corresponding toany one of a plurality of respective particle size ranges, means foroperating said selecting means to successively select signals having thecharacteristic corresponding to each size range, and means respective tosaid successively selected signals for recording a graph correspondingto said successively selected signals for each size range.

References Cited UNITED STATES PATENTS 2,494,441 1/1950 Hillier 235922,704,633 3/1955 Strother 23592 2,847,268 8/1958 Cowper 235-92 3,127,5053/1964 Gustavson 23592 MAYNARD R. WILBUR, Primary Examiner. JOHN F.MILLER, G. I. MAIER, Examiners.

1. A PARTICLE DISTRIBUTION PLOTTING APPARATUS COMPRISING: PARTICLEDETECTING ORIFICE MEANS PROVIDING A SIGNAL FOR EACH DETECTED PARTICLE,EACH SIGNAL HAVING A PARAMETER WHICH IS A FUNCTION OF THE SIZE OF EACHRESPECTIVELY DETECTED PARTICLE, PARTICLE DETECTION CONTROL MEANS COUPLEDTO SAID PARTICLE DETECTING ORIFICE MEANS AND RECEIVING EACH SAID SIGNAL,AND SAID DETECTION CONTROL MEANS PASSING FROM AN OUTPUT THEREOF ONLYSIGNALS REPRESENTING PARTICLES WITHIN A PREDETERMINED SIZE RANGE,PROGRAMMING MEANS COUPLED TO SAID PARTICLE DETECTION CONTROL MEANS ANDREGULATING SAID SIZE RANGE,